Then reconnect to your wireless network. After the first boot – when the system is installed – repeat the command above, just once.

By the way, this is not a new issue. I experienced this on Fedora 25, but curiously at the time the installer (the live system actually) worked fine. Just the installed system suffered from it. Now, with F26, it happened since the beginning. Here’s the bugzilla entry: https://bugzilla.redhat.com/show_bug.cgi?id=1154200.